Damselfish Family

This group of Damselfish make up the fourth installation of my fish coloring book. I’m fairly confident we’ll get to see some Sergeant Major fish when we go snorkeling, but many of the others are included here because they are beautiful (especially the juveniles) and should be fun to color.

You can read about this project in the post “A Fish Journal for a six-year-old” and you can see all the posts for this project using the tag “Fish Coloring Book“.

Learn about the Damselfish Family

Damselfish are small (usually less than six inches long at most) and the juveniles are often brightly colored. They like to live in, under, and around coral reef structures for shelter, protection, and food. Once a damselfish establishes its territory, it will only leave that area to chase off an intruder. Although almost all Damselfish defend their territory, some species defend their territory more fiercely than others.

Damselfish have several good reasons to defend their territory so well – there’s a lot at stake inside their homes. One reason for their behavior is to protect their offspring; Damselfish males defend their egg clusters inside their territory. Another reason for their territorial behavior is to protect their food source. Male and Female damselfish will actually farm patches of specific species of algae for food.

Although Damselfish are omnivorous (they eat plants and other animals) they especially like a certain type of filamentous red algae called “Polysiphonia”. This algae is very soft and fuzzy-looking – this is because it doesn’t have the harder, fibrous tissues that other types of algae have – making this the only algae that damselfish can digest. Because this species of algae is so important to Damselfish, they will find and establish their territories where this algae grows. Once they establish their territory, damselfish will not only keep out other algae-eating fish and reef creatures, they will actually weed out other species of algae so only the Polysiphonia will grow. This type of relationship is called a mutualistic relationship because both species benefit; the damselfish has a steady, reliable food source and the algae gets protected from being overgrown by other types of algae and – even though it gets eaten by the damselfish, it is protected from being totally consumed by other herbivores (plant eaters) on the reef, resulting in an overall net gain for the algae.

Even more amazing than this, in some places Damselfish have actually domesticated a species of shrimp. These shrimp get to live in the algae patch providing fertilizer for the algae with shrimp poop so the algae grow especially well. Damselfish will actually protect the shrimp from predators who might try to eat the shrimp living in its territory.